Peptide nucleic acids targeting miR-221 in human gliomas: uptake and modulation of miR-221 biological functions

MicroRNAs (miRNAs, miRs) are a family of small (19 to 25 nucleotides in length) noncoding RNAs that regulate gene expression by sequence-selective targeting of mRNAs, leading to a translational repression or mRNA degradation, depending on the degree of complementarity between miRNAs and the target sequences. Since a single miRNA can target several mRNAs and a single mRNA may contain several signals for miRNA recognition. In general, a low expression of a given miRNA is expected to be potentially linked with an ccumulation of targets mRNAs; conversely, a high expression of miRNAs is expected to be the cause of a low expression of the target mRNAs. The oncomiR miR-221 is highly expressed in human gliomas. In the first part of our study, human glioma cell lines U251, U373 and T98G were first characterized with respect to expression of miR-221 and compared with two breast cancer cell lines (MCF7 and MDA-MB-231) and the chronic myeloid leukemia K562 cell lines. In order to alter the biological functions of miR-221, a peptide nucleic acid targeting miR-221 (R8-PNA-a221) was produced and linked to an arginine-rich peptide (R8) to facilitate uptake by glioma cells. The effects of R8-PNA-a221 were analyzed in U251, U373 and T98G glioma cells and found to strongly inhibit miR-221. In addition, the effects of R8-PNA-a221 of p27Kip1 RT-qPCR and by Western blotting. No change of p27Kip1 in U251 cells in the presence of PNA-a221 (lacking the R8 peptide), whereas significant increase of p27Kip1 These data were confirmed by Western blot assay; a clear increment of p27kip1 protein expression in the sample treated with A8-PNA-a221 was detected. Our results suggest that PNAs against oncomiRNA miR-221 might be proposed for experimental treatment of human gliomas. (a target of miR-221) were analyzed in U251 cells by mRNA was observed with the R8-PNA-a221